1. Field of the Invention
The present invention relates to a dielectric filter which can be used in various applications, such as a communication system.
2. Description of Prior Art
In order to obtain desirable filter characteristics, a typical prior art dielectric filter, as shown in FIG. 5 and FIG. 6, has a structure, wherein a plurality of dielectric coaxial resonators 1 are electrically connected in parallel in such a manner that metal connectors 3 are connected in parallel through first capacitors 17 formed on an alumina ceramic substrate 22. Substrate 22 is provided with input-output terminals 2. A series connection of a second capacitor 18, a strip line 23 and a third capacitor 20 is formed on an attenuation pole substrate 21 and is connected in parallel relative to the first capacitors 17.
However, the conventional filter of the above arrangement has a drawback in that the alumina ceramic substrate 22 and the attenuation pole substrate 21 are assembled in a double stage construction. This results in a large size. In addition, it is difficult to keep the alumina ceramic substrate 21 and the attenuation pole substrate 21 parallel with each other. This difficulty increases the number of man-hours required in the assembly stage.